What is it?

The less expensive diesel version found in the third-generation Mini line-up. Up front there’s a 1.5 litre, 3-cylinder diesel engine, the same that can be found in the more powerful and costly Cooper D.

It features common-rail direct injection and a "TwinPower" turbocharger that, in this case, means a variable geometry turbine.

Differences to the more powerful Cooper D variant can only be found inside the engine’s electronic management system, so the One D’s hardware is exactly the same.

The ECU decreases power from 114bhp to 94bhp and maximum torque from 199lb ft to 162lb ft. Fuel economy also improves, from a claimed average of 80.7 mpg to 83.1 mpg.

The One D’s basic list price is also £1560 cheaper than the Cooper D, but it still costs £1140 more than the entry level petrol version, the 1.2-litre Mini One.

What's it like?

As is usually the norm with press cars, our test vehicle was laden with optional items – but looking beyond that, for a moment, there is no sign that this is an entry level variant.

Cabin quality is the same as in more expensive Minis, with a strong sense of robustness and a solid feel to most of the materials used inside, with just the right amount of soft-touch plastics.

The centre console keeps the oval display from the previous model, even if the speedometer is no longer there. The driving position is near perfect, lower than in most superminis and with an almost vertical steering wheel.

The 6-speed manual gearbox sampled here has a nice mechanical feeling and pedals have the right weight. The diesel engine is very refined; you really need to step outside the car to hear to the typical clatter.

There are no vibrations coming from the three pot, either, unless you push it all the way to the redline, which is missing the point in a car like this.

Make no mistake, though, this is still very much a Mini in the sense that dynamically it is always ready to play. Ask it to turn sharply and it will obey with gusto.

But the One D is foremost made for city driving. In slow-moving traffic there is no lack of torque at low and middle revs, and the engine is always smooth and strong. Sometimes its very low noise output even makes the driver forget that there are other ratios above third and fourth to choose from.

The Mini's suspension still isn’t the most comfortable in the segment but is otherwise tolerable, and the test car’s energy saver tyres are perfectly adequate for the mission at hand.

In town, the claimed average 72.3 mpg fuel economy felt realistic but where it really impressed was on the motorway, where we reached 72.4 mpg with ease. The three available driving modes – Sport, Mid and Green – really do make a difference, though it’s only in the latter that you’ll see the kind of economy achieved here.

Of course, with this kind of power-to-weight ratio, do not expect much in terms of performance. It's when your start to push on a little bit, outside town, that you realise this is not a Cooper D.

Should I buy one?

If you need a diesel and you don’t spend much time outside town, and you don't mind paying a premium, the Mini One D may be the car for you.

For those who cover more motorway or B-road miles, the Cooper D would be the more obvious choice, trading fuel economy for better performance on the open road.

£1,200 more expensive, heavier, slower, noisey, rougher than the 1.2 petrol. If you did 10,000 miles a year (maybe more than average for this sort of car) wonder how long it would take to pay for itself?? You'd still be left with a slower, noisey, more complicated etc car

If you used this diesel for mainly city driving then the short distances would mean you'd have to have the Particulate Filter in the exhaust replaced at vast expense several times as you'd never get the exhaust hot enough for it to self-clean, and the diesel fumes would help poison the residents, as Hilton Holloway has pointed out several times in his campaigns - recommending diesel cars for city use isn't really ethical.

Autocar wrote:

In town, the claimed average 72.3 mpg fuel economy felt realistic but where it really impressed was on the motorway, where we reached 72.4 mpg with ease.

Only 0.1mpg difference between town and motorway? really - or is that a typo?

Only 0.1mpg difference between town and motorway? really - or is that a typo?

This is just the difference between claimed and actual fuel consumption.

The claimed extra-urban cycle, that you could class as motorway, is over 91 mpg. They're saying they actually got 72.4 mpg in real world conditions. Presumably that would put the urban/town return at a realistic 55 mpg from the claimed 72?

If you used this diesel for mainly city driving then the short distances would mean you'd have to have the Particulate Filter in the exhaust replaced at vast expense several times as you'd never get the exhaust hot enough for it to self-clean, and the diesel fumes would help poison the residents, as Hilton Holloway has pointed out several times in his campaigns - recommending diesel cars for city use isn't really ethical.
It amazes me how many motoring journalists still recommend diesel cars for city use (this review goes on to say that if you don't spend much time outside town then the One D may be the car for you), and never refer to the problems you mention. Its as if they don't exist.

If you used this diesel for mainly city driving then the short distances would mean you'd have to have the Particulate Filter in the exhaust replaced at vast expense several times as you'd never get the exhaust hot enough for it to self-clean, and the diesel fumes would help poison the residents, as Hilton Holloway has pointed out several times in his campaigns - recommending diesel cars for city use isn't really ethical.

It amazes me how many motoring journalists still recommend diesel cars for city use (this review goes on to say that if you don't spend much time outside town then the One D may be the car for you), and never refer to the problems you mention. Its as if they don't exist.

I'll start it off. I just don't know how they get away with calling this a MINI. It's now so huge it should at least be called MAXI, but even that doesn't describe this bloated mass. They should just call it GIGANTIC!! Maybe that would that please all those that believe the MINI name can only be applied to the tiny original??

Or was that just what the trip computer read? My experience is that trip computers are not precision instruments (one importer once mistakenly calibrated one to read US mpg, not imperial), and I suspect some are deliberately programmed to produce optimistic figures to please the buyers in the same way that speedometers do. So unless Autocar has taken the trouble to calibrate the trip computer against carefull brim to brim measurement over a respectable distance, I'd treat this observed reading with a pinch of salt. In any case, it means nothing without knowing the cruising speed, mean gradient, wind strength and direction, vehicle loading, temperature etc...